Controlling apparatus of an electric oven and controlling method of the same

ABSTRACT

Disclosed are apparatus and method for controlling an electric oven, capable of operating heaters in an optimized state by changing a heater-on time of the heater in an operation interval of the heater which is periodically turned on/off.

TECHNICAL FIELD

The present invention relates to an electric oven, and particularly toapparatus and method for controlling an electric oven, which control aheater of the electric oven so that a suitable temperature may be keptin the oven with supplying electricity in an optimized state. Moreparticularly, the present invention relates to apparatus and method forcontrolling an electric oven, which are capable of keeping an optimizedelectricity supplying state and an optimized temperature state for theoven by controlling an on-time of the heater at which the heater isturned on.

BACKGROUND ART

Generally, an electric oven is a utensil for keeping a temperature in acavity suitably by heating of a heating wire. In particular, a pluralityof heaters are prepared at upper, lower and side surfaces in the cavityso that the inside of the cavity may be three-dimensionally heated.Furthermore, a magnetron may be additionally installed to one side ofthe inner circumference of the cavity so that foods are cooked byelectronic waves generated by the magnetron.

In the electric oven, the most important thing is to keep a temperaturein the cavity at a desired level. In order to keep a suitabletemperature in the cavity as mentioned above, a plurality of heaters aregenerally repeatedly turned on and off. For example, if a currenttemperature in the cavity is not higher than a set temperature, theheaters are turned on/off at a set interval so that the inside of thecavity is heated up to the set temperature. On the while, if a currenttemperature is higher than the set temperature, the heaters are turnedoff, not to give heat into the cavity.

However, since the conventional heat controlling method controls theoven by turning off the heaters if a temperature in the cavity is high,but turning on/off the heaters at a set interval if the temperature inthe cavity is low, there may be caused local overheating. In addition,since the electricity is instantly turned on/off, a breaker switch maybe turned off.

Moreover, since the heaters are operated at a predetermined fixedperiod, it is impossible to accurately satisfy an optimal operatingcondition suitable for various circumstances. In more detail, as anexample, if a temperature in the cavity is approaching a settemperature, a heater with small heating capacity is generally operated,but even in this case, the heating capacity should be controlled inconsideration of an amount of the foods received in the cavity. However,since the heaters operated at a given interval, the temperature in thecavity may be continuously decreased due to their small capacity when alot of foods are received in the cavity. On the while, if an amount offoods is small, the heater may be so frequently turned off, therebyprobably causing a problem in the circuit of the electric oven or thedomestic circuit breaker.

DISCLOSURE OF THE INVENTION

The present invention is designed to solve the problems of the priorart, and therefore an object of the invention is to provide apparatusand method for controlling an electric oven, which are capable ofcontrolling an inner temperature of the electric even to an optimizedstate by making a heater operation interval and a heat-on time bevariable according to a temperature in a cavity of the electric ovenwhen heaters in the electric oven are controlled.

In addition, the present invention is directed to providing apparatusand method for controlling an electric oven, which keep a suitabletemperature in the cavity of the electric oven with the use of manyheaters by turning on a heater giving much influence on the temperatureat a low temperature so that the temperature reaches a desired levelwithin a short time and turning on a heater giving small influence onthe temperature when it is desired to keep a suitable temperature.

In addition, the present invention is directed to providing apparatusand method for controlling an electric oven with the use of manyheaters, which are capable of controlling the heaters always in anoptimized state by operating the heaters in an alternate andsimultaneous manner in consideration of electric power.

In order to accomplish the above object, the present invention providesan apparatus for controlling an electric oven, which includes a keymanipulation unit for manipulation of the electric oven; a controllerfor controlling a temperature in a cavity of the electric oven to a settemperature according to a signal of the key manipulation unit; and atleast one heater operated at a predetermined heating on/off interval bymeans of the controller, a heater-on time in the heating on/off intervalof the heater being changed at a predetermined period with comparing acurrent temperature in the cavity with the set temperature.

In another aspect of the invention, there is provided a method forcontrolling an electric oven, which includes the steps of comparing acurrent temperature in the electric oven and a set temperature; andheating the electric oven by turning on/off at least one heater at apredetermined interval, wherein a heater-on time of the heater iselongated according to a temperature difference obtained in thecomparing step.

In still another aspect of the invention, there is also provided anapparatus for controlling an electric oven, which includes a keymanipulation unit for manipulation of the electric oven; at least oneheater formed in the electric oven; and a controller for operating theheater according to a signal of the key manipulation unit so that theheater is turned on/off at a predetermined interval, and changing aheater-on time of the heater in the heating on/off interval according toa difference between a current time in the electric oven and a settemperature.

By using the present invention, the electric oven may always keep atemperature in the cavity of the electric oven into an optimized state.Particularly, the internal state of the cavity may be kept in anoptimized state regardless of an amount of foods in the cavity or a settemperature.

In addition, since the heaters may be turned on/off in an optimizedstate suitable for the temperature state in the cavity, the electricoven which consumes high electric power may be operated in an optimizedelectric power state.

Moreover, since the electric oven is operated with an optimized electricpower, the power interruption problem may be solved. In particular, thepower supply in the oven may be safely operated, and malfunction of theoven may be prevented.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention.

In the drawings:

FIG. 1 is a block diagram showing an electric oven according to oneembodiment of the present invention;

FIG. 2 is a flowchart for illustrating a method for controlling theelectric oven according to the present invention; and

FIG. 3 is a flowchart for illustrating a method for controlling anelectric oven with a plurality of heaters therein, according to thepresent invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, preferred embodiments of the present invention will bedescribed in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram showing an electric oven according to oneembodiment of the present invention.

Referring to FIG. 1, the electric oven according to the spirit of thepresent invention includes a key manipulation unit 2 for manipulatingoperation of the electric oven by manipulation of a user, a sensor 3 fordetecting humidity or temperature of foods, a controller 1 which storesan automatic cooking control program and various cooking data in advanceand controls the overall operation of the electric oven according to asensing signal of the sensor 3, a display 4 for displaying a controlstate of the electric oven by control of the controller 1, first, secondand third heaters 5, 6 and 7 operated by control of the controller 1,and a fan 8 for cooling of electric components and convection inside acavity of the electric oven.

In detail, the electric oven of the present invention is configured asfollows.

A temperature control function key provided on the key manipulation unit2 may be used for simultaneously designating temperature and humidity inthe cavity by one pushing, and it is also possible that a temperaturecontrol key and a humidity control key are independently provided. Inaddition, the sensor 3 is a temperature sensor positioned at any pointin the cavity, and one or more sensor may be used for measuring atemperature in the cavity. The display 4 may displaytemperature/humidity in the cavity, an operation state of the electricoven, or a cooking state designated in the electric oven. The fan 8 mayinclude a cooling fan for electric components in the electric oven and aconvection fan in the cavity, and the fan 8 is controlled by thecontroller 1.

In addition, the heaters 5, 6 and 7 may be arranged so that a heatergiving more influence on temperature is positioned at an upper portionof the cavity and a heater giving less influence on temperature ispositioned around the cavity. By such arrangement, a plurality ofheaters may be suitably controlled according to their influence ontemperature, and a temperature in the cavity may also be managedsuitably.

In addition, the controller 1 allows the sensor 3 to sense an operatingstate of the electric oven and also makes the electric oven becontrolled into a suitable state by means of an instruction input by thekey manipulation unit 2. Moreover, the controller 1 generates andtransmits a predetermined operating signal so that the display 4, theheaters 5, 6 and 7 and the fan 8 may be operated suitably.

Now, operation of the electric oven according to the present inventionwill be described.

If a user selects a temperature control function key through the keymanipulation unit 2, in case the controller 1 turns on/off one heater,the controller 1 changes and controls a heater control period and aheater-on time so that a temperature in the electric oven may beoptimized as desired within the minimum time. In addition, in case thecontroller 1 turns on/off several heaters, the controller 1 makes ‘afull on’ for turning on all heaters such as the first heater 5, thesecond heater 6 and the third heater 7 if the temperature in the cavityis low, while the controller 1 turns on the small number of heaters ormakes the heater-on time to the minimum so that the temperature in theelectric oven may be controlled to an optimized state if the temperaturein the cavity is high. That is to say, in case of turning on/off severalheaters, the controller 1 turns on a heater giving much influence ontemperature in an initial stage at a low temperature so that thetemperature may reach a desired level, while the controller 1 turnson/off a heater giving small influence on temperature when it isrequired to keep a proper temperature.

In addition, in case several heaters are turned on/off by the controller1, the heaters 5, 6 and 7 are operated alternately or simultaneously inconsideration of the electric power so that a room circuit breaker isnot turned off due to abrupt change of an excess current, and thetemperature in the cavity may be controlled into an optimized statewithin a minimum time.

Meanwhile, the present invention has a distinctive feature in a way ofcontrolling the heaters 5, 6 and 7. That is to say, when the heaters 5,6 and 7 are controlled, a heater-on time is not fixed but changedaccording to a temperature in the cavity. For example, if thetemperature in the cavity is high, the heater-on time of the heaters 5,6 and 7 is elongated so that more heat is applied into the cavity,while, if the temperature in the cavity is near a set temperature andnot so much heat is needed, the heater-on time of the heaters 5, 6 and 7is shortened so that a suitable amount of heat is applied into thecavity. Adjusting the heater-on time of the heaters as mentioned abovemay be called ‘a heater cycle control algorithm’.

In addition, in case a plurality of heaters are used in the electricoven, a different control method may be used. That is to say, if a largeamount of heat is required since the temperature in the cavity issignificantly different from the set temperature desired by a user at aninitial heating stage, a large number of heaters are turned on so as toapply a large amount of heat into the cavity. However, if thetemperature in the cavity is approaching the set temperature, a smallnumber of heaters are turned on so as to apply a small amount of heatinto the cavity.

As mentioned above, an individual cycle control algorithm and aselective operation of the heater may be conducted for each heateraccording to the difference between the set temperature and thetemperature in the cavity, and such selective operation of the heatersmay make the temperature and/or humidity state in the cavity into anoptimized state within a shortest time.

FIG. 2 is a flowchart for illustrating the method for controlling theelectric oven according to the present invention. The electric ovencontrolling method according to this embodiment proposes a heater cyclecontrol algorithm which variably controlling the heater control cycleand the heater-on time in order to control the temperature in theelectric oven into a desired state within a shortest time.

Referring to FIG. 2, it is determined at first whether a currenttemperature in the cavity is lower than the set temperature over 200° C.(S41). If it is, 10 seconds are added to the current heater operationcycle and the heater-on time is also added by 10 seconds (S42) so thatthe temperature in the cavity may reach a suitable temperature within ashortest time. The time extended in the operation cycle of the heatermeans that the heater-on time is extended. Thus, it may be consideredthat the heater-on time is elongated while a heater-off time is kept asit is, and this resultantly increases a heating capacity of the heater.Of course, a process of setting a set temperature and/or a set time by auser is conducted in advance before comparison between the temperaturein the cavity and the set temperature. In order to set the settemperature, the user may push a dial button or a cooking buttonprogrammed in advance, or use various other ways.

With the heater-on time being extended, the heater is operated duringthe set time (S50). Then, it is determined whether a promised time forcooking foods is passed (S51). If the promised time is not passed, theprocess is returned to the step of comparing a current temperature inthe cavity with the set temperature (S41), thereby conducting theelectric oven controlling method of the present invention continuously.Of course, if the cooking time is passed, the electric oven controllingmethod is not conducted any more, but finished.

Meanwhile, the heater operating step (S50) may be accomplished during apredetermined time. If an operation time of the heater is too long, thetemperature in the cavity may be not controlled rapidly. On the while,if the operation time of the heater is too short, the electricityconsumed may be too abruptly changed. Thus, it is preferable that theheater operating step (S50) is continued for about 1 minute. Inaddition, the cooking time may be set in advance in the step ofdetermining whether the cooking time is passed (S51), set individuallyby the user, or previously acknowledged according to the preset program.

And then, it is determined whether a current temperature in the cavityis higher than 200° C. below the set temperature but lower than 100° C.of the set temperature (namely, the current temperature+100° C.<the settemperature<the current temperature+200° C.) (S43). If it is, the heateroperation cycle and the heater-on time are shortened since thetemperature difference has been decreased. In more detail, 5 seconds areadded to the cycle and the heater-on time is also added by 5 seconds(S44). After that, the heater operating step (S50) is conducted, andwhether the cooking time is passed is determined.

In addition, it is also determined whether a current temperature in thecavity is lower than the set temperature as much as about 50° C.(namely, the current temperature+50° C.<the set temperature<the currenttemperature+100° C.) (S45). If it is, 2 seconds are added to the currentcycle and the heater-on time is also added by 2 seconds (S46). Afterthat, the heater operating step (S50) is conducted, and whether thecooking time is passed is determined.

And then, it is determined whether a current temperature in the cavityis less than the set temperature in the range less than 50° C. (S47). Ifit is, the heater operation cycle currently applied is kept as it is sothat the heater is operated continuously (S48). In addition, if acurrent temperature in the cavity is higher than the set temperature,the heater is turned off for about 6 seconds (S49). Since the heaterturns off, the current temperature in the cavity may be lowered belowthe set temperature. Of course, if the heater is turned off for apredetermined time, the heater is operated according to the currentheater operation cycle (S50), whether the promised time is passed isdetermined (S51), and then the operation of the electric oven isaccomplished continuously.

Meanwhile, it is also possible that the heater-off time is changed whena current temperature in the cavity is higher than the set temperatureaccording to the difference between the current temperature and the settemperature so that the temperature in the cavity may be more suitablycontrolled. For example, if the heater is turned off for 6 seconds whena current temperature in the cavity is higher than the set temperatureas much as 10° C., the heater may be turned off for 12 seconds when thetemperature difference is 20° C. It may be easily expected that theheater may be turned off for a longer time if the temperature differenceis larger.

This electric oven controlling method may continuously control theelectric oven by repeatedly executing the step of determining whether itreaches the promised time (S51).

For example, if the current heater cycle turns on the heater for 5seconds and turns off the heater for 5 seconds, the current temperaturein cavity is 50° C. and the set temperature is 300° C., after the heatercycle control algorithm of the present invention is passed once, theheater-on time becomes 15 seconds and the heater-off time becomes 5seconds due to the comparison step (S41) and the cycle changing step(S42). In addition, after the heater is operated once according to thecycle (heater-on 15 seconds and heater-off 5 seconds) during the heateroperating step (S50), the heater cycle control algorithm is accomplishedonce again. At this time, if a current temperature in the cavity is 80°C., the heater-on time becomes 25 seconds and the heater-off timebecomes 5 seconds due to the comparison step (S41) and the cyclechanging step (S42). By executing the steps repeatedly, the heater maybe operated with continuously changing the heater operation cycle towardan optimized state.

In addition, classification of temperature in the cavity and a timeadded to the heater operation cycle described in this embodiment arejust one example, and they may be suitably modified according to adetail specification of the electric oven and a capacity of the heater.However, the spirit of the present invention that a temperature in thecavity may be rapidly and suitably changed and controlled bycontinuously changing the heater operation cycle by means of the step ofcomparing the current temperature in the cavity with the set temperatureshould be not changed. The heater controlling method which activelychanges the heater operation cycle by comparing the current temperaturein the cavity with the set temperature may be called ‘a heater cyclecontrol algorithm’. Furthermore, if the difference between the currenttemperature in the cavity and the set temperature is decreased less thana certain level, the heater operation cycle may be even decreased so asto prevent foods from being spoiled.

Meanwhile, in case the controller of the electric oven turns on/offseveral heaters in such a way, the controller may turns on all ofheaters (e.g., first, second and third heaters) when a temperature inthe cavity is far lower than the set temperature (which is called ‘fullon’), while, if the temperature in the cavity is high, the controllermay reduce the heater operation cycle and shortens the heater-on time tothe minimum so that the temperature in the electric oven may becontrolled to its optimized state. In the same point of view, in casethe controller turns on/off several heaters, the controller may turn ona heater giving much influence on temperature firstly so that thetemperature is increased up to a desired level within a shortest time,while the controller may turn on a heater giving less influence ontemperature when the temperature in the electric oven should be kept ata suitable temperature.

FIG. 3 is a flowchart for illustrating a method of controlling anelectric oven in case a plurality of heaters are installed in theelectric oven. This flowchart shows a method for controlling operationof heaters in case a plurality of heaters are installed in the electricoven, and this embodiment exemplifies the case that three heaters areinstalled.

Referring to FIG. 3, there are four temperature comparison steps(S61)(S63)(S65)(S67) like the case of FIG. 2, and the controller 1executes heater operation steps (S62)(S64)(S66)(S68)(S69) respectivelydepending on the comparison results conducted by the temperaturecomparison steps. Of course, a step of operating the heaters during aset time (S70) and a step of determining whether a cooking time ispassed (S71) may be conducted in the same way as the case of FIG. 2.However, this embodiment is different from the former embodiment justfor the point that the heater operation steps (S62)(S64)(S66)(S68)(S69)are conducted.

In detail, the kind of operated heaters is different according to thedifference between a current temperature in the cavity and the settemperature, which is compared in the temperature comparison steps(S61)(S63)(S65)(S67). For example, all of the first, second and thirdheaters are operated according to the heater cycle control algorithm(S62) in case the difference between a current temperature in the cavityand the set temperature is greatest, the first and second heaters areoperated according to the heater cycle control algorithm (S64) in casethe difference between the current temperature in the cavity and the settemperature is great but less than the above case, only the first heateris operated according to the heater cycle control algorithm (S66) incase the difference between the current temperature in the cavity andthe set temperature is less than the above case, and only the thirdheater is operated according to the heater cycle control algorithm (S68)in case the difference between the current temperature in the cavity andthe set temperature is very small less than the above case. Of course,if the set temperature is less than the current temperature in thecavity, all heaters are turned off for a predetermined time (S69).

As described above, in case several heaters are turned on/off in theelectric oven, a plurality of heaters are selectively turned on/off inconsideration of the difference between a current temperature in thecavity and the set temperature, thereby increasing the temperature inthe cavity rapidly up to an optimized level and keeping the optimizedtemperature for a long time accurately.

In addition, in case of several heaters are turned on/off, the heatersare operated in an alternate or simultaneous manner in consideration ofthe electric power so that a circuit breaker is not turned off and thetemperature in the cavity may be controlled into an optimized statewithin a minimum time.

The present invention has a distinctive feature that operation time ofone or several heaters installed in the electric oven is suitablycontrolled according to the difference between a current temperature inthe cavity and the set temperature.

In detail, in a series of heater operation cycles for turning on/offheater(s), the heater-on time is suitably changed and adjustedcontinuously according to the difference between a current temperaturein the cavity and the set temperature with keeping the heater-off timeas it is so that the electric oven may keep its optimizedtemperature/humidity state.

There may be proposed another preferably embodiment by modifying theabove embodiments. For example, the steps of comparing a currenttemperature in the cavity and the set temperature may be divided intomore numbers according to the number of heaters. In detail, the heatercontrol cycle may be classified into many steps, more than four stepsproposed in FIG. 2. In addition, in case a plurality of heaters areapplied, a heater state selected according to the number of heaters maybe selected according to combination of the heaters. For example, incase three heaters are installed, seven combinations may be selected forthe heaters in addition to one case that all heaters are turned off.

In addition, the heater-on time conducted in the heater operation steps(S50)(S70) may be changed according to usage of the electric oven.However, since the heater control algorithm is conducted whenever theheater operation time conducted in the heater operation step is passed,the heater-on time may be continuously increased. Thus, it is apparentthat the heater operation cycle is continuously changed whenever theheater operation time is passed.

In addition, since the heater-off time is changed according to thedifference between the set temperature and the current temperature inthe cavity higher than the set temperature, it is possible to reach anoptimized temperature more rapidly.

In addition, the set temperature may be set by a user in advance, or theset temperature may also be set automatically by a stored program incase the user selects a programmed cooking menu.

In addition, in case a plurality of heaters having different heatingcapacities in comparison to electric power are used, the heaters may bealternately or simultaneously operated though the same heating capacityis required.

INDUSTRIAL APPLICABILITY

As described above, the present invention enables to always keep atemperature in the cavity of the electric oven into an optimized state.Particularly, the internal state of the cavity may be kept in anoptimized state regardless of an amount of foods in the cavity or a settemperature.

In addition, the same control method may be applied to other heatingdevices in addition to an electric oven for the purpose of keeping asuitable temperature/humidity state.

Moreover, since the electric oven is operated with an optimized electricpower, the power interruption problem may be solved. In particular, thepower supply in the oven may be safely operated, and malfunction of theoven may be prevented.

1. An apparatus for controlling an oven, comprising: an input unit forinputting a set temperature of the oven; at least one heater whichoperates with a variable heating on/off cycle, the variable heatingon/off cycle including a heater-on time and a heater-off time; and acontroller for adjusting the heating on/off cycle such that after the atleast one heater operates for a current cycle period with a currentheating on/off cycle, the controller generates a new heating on/offcycle by adjusting the heater-on time of the current heating on/offcycle based on a difference between a current temperature in the ovenand the set temperature, the at least one heater operating with the newheating on/off cycle in a next cycle period.
 2. The apparatus accordingto claim 1, wherein a heating-off time in the heating on/off cycle isfixed.
 3. The apparatus according to claim 1, wherein the at least oneheater includes a plurality of heaters, as a result of comparisonbetween the current temperature in the oven and the set temperature, atleast one of the heaters with greater heating capacity being turned onif a temperature difference is greater than a predetermined criterion,at least one of the heaters with smaller heating capacity being turnedon if the temperature difference is smaller than the predeterminedcriterion.
 4. The apparatus according to claim 1, wherein the at leastone heater includes a plurality of heaters, as a result of comparisonbetween the current temperature in the oven and the set temperature, allof the heaters being turned off for a predetermined time if the settemperature is lower than the current temperature in the oven.
 5. Theapparatus according to claim 1, wherein as a result of comparisonbetween the current temperature in the oven and the set temperature, theheater-on time of the heater in the new heating on/off cycle iselongated as the set temperature is higher than the current temperaturein the oven.
 6. The apparatus according to claim 1, wherein, after thenext cycle period is completed, the controller generates a second newheating on/off cycle by adjusting the heater-on time of the next heatingon/off cycle based on a new difference between the current temperaturein the oven and the set temperature.
 7. The apparatus according to claim1, wherein, as a result of comparison between the current temperature inthe oven and the set temperature, the next heating on/off cycle isunchanged if the difference between the current temperature and the settemperature is not more than a predetermined criterion.
 8. The apparatusaccording to claim 1, wherein the set temperature is manually set by auser.
 9. The apparatus according to claim 1, further comprising a sensorfor measuring the current temperature in the oven.
 10. The apparatusaccording to claim 9, further comprising means for comparing the currenttemperature in the oven measured by the sensor and the set temperatureand obtaining the difference between the current temperature in the ovenand the set temperature.
 11. The apparatus according to claim 10,wherein the controller includes means for adjusting the heater-on timeof the current heating on/off cycle based on the difference between thecurrent temperature in the oven and the set temperature obtained by thecomparing means.
 12. The apparatus according to claim 11, wherein theadjusting means adds one of a plurality of predetermined time periods tothe heater-on time of the current heating on/off cycle as the heater-ontime of the new heating on/off cycle when the difference between thecurrent temperature in the oven and the set temperature is larger than acorresponding one of a plurality of predetermined values.
 13. Theapparatus according to claim 1, wherein the controller adds one of aplurality of predetermined time periods to the heater-on time of thecurrent heating on/off cycle as the heater-on time of the new heatingon/off cycle when the difference between the current temperature in theoven and the set temperature is larger than a corresponding one of aplurality of predetermined values.
 14. A method for controlling an oven,comprising: heating the oven by operating at least one heater with acurrent heating on/off cycle in a current cycle period, the currentheating on/off cycle including a heater-on time and a heater-off time;after the current cycle period is completed, generating a new heatingon/off cycle by adjusting the heater-on time of the current heatingon/off cycle based on a difference between a current temperature in theoven and a set temperature; and operating the at least one heater withthe new heating on/off cycle in a next cycle period.
 15. The methodaccording to claim 14, further comprising turning on the heaters as thecurrent temperature in the oven is lower than the set temperature. 16.The method according to claim 14, further comprising turning on a heaterwith greater heating capacity among the heaters as the currenttemperature in the oven is lower than the set temperature.
 17. Themethod according to claim 14, wherein, in the heating step, a pluralityof heaters are alternately or simultaneously operated in considerationof electric power.
 18. The method according to claim 14, wherein theheater-on time of the heater is adjusted after each heating on/off cycleis completed.
 19. The method according to claim 14, wherein, in theheating step, the heaters to be operated are selected by a smallernumber of combinations than the number of cases of a subset for thenumber of the heaters.
 20. The method according to claim 14, wherein thegenerating step includes elongating the heater-on time of the heater inthe new heating on/off cycle as the current temperature is lower thanthe set temperature.
 21. The method according to claim 14, furthercomprising, after the next cycle period is completed, generating asecond new heating on/off cycle by adjusting the heater-on time of thenext heating on/off cycle based on a new difference between the currenttemperature in the oven and the set temperature.
 22. The methodaccording to claim 14, further comprising turning on all of the heatersfor a predetermined time if the current temperature is higher than theset temperature.
 23. The method according to claim 14, furthercomprising keeping the next heating on/off interval of the heaterunchanged if the difference between the current temperature and the settemperature is not more than a predetermined criterion.
 24. The methodaccording to claim 14, wherein the step of generating the new heatingon/off cycle includes adding one of a plurality of predetermined timeperiods to the heater-on time of the current heating on/off cycle to bethe heater-on time of the new heating on/off cycle when the differencebetween the current temperature in the oven and the set temperature islarger than a corresponding one of a plurality of predetermined values.25. An apparatus for controlling an oven, comprising: an input unit forinputting a set temperature of the oven; a plurality of heaters locatedin the oven, each of the heaters operating with a variable heatingon/off cycle, the variable heating on/off cycle including a heater-ontime and a heater-off time; and a controller for selectively turningon/off the heaters based on a difference between a current temperaturein the oven and the set temperature, when at least one of the heaters isselected to turn on, and for adjusting the heating on/off cycle suchthat after the at least one of the heaters operates for a current cycleperiod with a current heating on/off cycle, the controller generates anew heating on/off cycle by adjusting the heater-on time of the currentheating on/off cycle based on the difference between the currenttemperature in the oven and the set temperature, the at least one of theheaters operating with the new heating on/off cycle in a next cycleperiod.
 26. The apparatus according to claim 25, wherein the heating ontime of the new heating on/off cycle is elongated as the set temperatureis higher than the current temperature.
 27. The apparatus according toclaim 25, further comprising a sensor for measuring the currenttemperature in the oven.
 28. The apparatus according to claim 27,further comprising means for comparing the current temperature in theoven measured by the sensor and the set temperature and obtaining thedifference between the current temperature in the oven and the settemperature.
 29. The apparatus according to claim 28, wherein thecontroller includes means for adjusting the heater-on time of thecurrent heating on/off cycle based on the difference between the currenttemperature in the oven and the set temperature obtained by thecomparing means.
 30. The apparatus according to claim 29, wherein theadjusting means adds one of a plurality of predetermined time periods tothe heater-on time of the current heating on/off cycle as the heater-ontime of the new heating on/off cycle when the difference between thecurrent temperature in the oven and the set temperature is larger than acorresponding one of a plurality of predetermined values.
 31. Theapparatus according to claim 25, wherein the controller adds one of aplurality of predetermined time periods to the heater-on time of thecurrent heating on/off cycle as the heater-on time of the new heatingon/off cycle when the difference between the current temperature in theoven and the set temperature is larger than a corresponding one of aplurality of predetermined values.